This invention relates to manual operation of an automatic transmission, and more specifically, relates to prevention of a speed-ratio variation due to malfunction or misoperation of a manual operation switch.
Tokkai Hei 11-99840 published by the Japanese Patent Office in 1999 discloses a device enabling manual operation of an automatic transmission of a vehicle. In order to perform this operation, the vehicle is provided with a manual operation switch attached to a shift lever and a manual operation switch attached to the steering wheel.
The shift lever sets operation ranges such as a drive range, a reverse range, a neutral range and a manual range.
In a manual range, If the shift lever is moved in the upshift or the downshift direction, the manual operation switch with which the shift lever is provided outputs an upshift/downshift signal corresponding to the motion of the shift lever, and a controller changes the speed ratio of the automatic transmission according to this signal.
The same operation as that of the shift lever can be performed by operating the manual operation switch attached to the steering wheel.
By this mechanism, in a vehicle provided with an automatic transmission, the operating environment of a manual transmission can be simulated.
The manual operation switch provided to the shift lever or the manual operation switch provided to the steering wheel do not output an upshift/downshift signal if the shift lever is not located in the manual range.
However, If the manual operation switch attached to the steering wheel is fixed in a position corresponding to upshift or downshift due to a fault of the switch or a misoperation of a driver of the vehicle, an unintended speed ratio variation will occur immediately after the driver moves the shift lever to the manual range, and the driver will experience an uncomfortable feeling.
It is therefore an object of this invention to prevent an upshift or downshift unintended by the driver due a fault or misoperation of the manual operation switch.
It is another object of this invention to enable manual operation of the transmission via the manual operation switch attached to the shift lever when there is a malfunction of the manual operation switch attached to the steering wheel.
In order to achieve the above objects, a manual operation control device for an automatic transmission for a vehicle according to this invention comprises a first switch which can select a manual mode. a second switch which can specify one of an upshift or a downshift, and a microprocessor programmed to change a speed ratio of the automatic transmission according to a specification of the second switch when the first switch has first selected the manual mode, and the second switch subsequently specifies one of the upshift and the downshift and prohibit a variation of the speed ratio of the automatic transmission according to the specification of the second switch when one of the upshift and the downshift is specified by the second switch at a timing not later than a timing at which the manual mode is selected by the first switch.
This invention also provides a manual operation control method for an automatic transmission for a vehicle wherein the transmission is provided with a first switch which can select a manual mode and a second switch which can specify one of an upshift or a downshift. The method comprises changing a speed ratio of the automatic transmission according to a specification of the second switch when the first switch has first selected the manual mode, and the second switch subsequently specifies one of the upshift and the downshift, and prohibiting a variation of the speed ratio of the automatic transmission according to the specification of the second switch when one of the upshift and the downshift is specified by the second switch at a timing not later than a timing at which the manual mode is selected by the first switch.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.